Various systems for connecting fastener elements (e.g., pedicle screws) to elongated supports (e.g., rods) for the purposes of vertebral fixation have been proposed. Examples include the systems described in the following U.S. patents.
U.S. Pat. No. 5,466,237 relates to a variable locking stabilizer anchor seat and screw. More particularly, this patent relates to a bone interface anchor provided for use with a stabilizer rod for the internal fixation of a spine. The anchor has a seat which accommodates the stabilizer rod and which receives a bone screw for the fixation of the seat to the bone. A compression member cooperates with the seat external to the stabilizer rod and can be tightened to cause a compressive force on the stabilizer rod. The stabilizer rod bears on a rounded surface of the bone screw so as to cause a mating interface between the seat and the bone screw. Subsequently, the position of the seat relative to the bone screw can be locked.
U.S. Pat. No. 5,474,555 relates to a spinal implant system. More particularly, this patent relates to an apparatus for the internal fixation of the spine. The apparatus comprises an assembly having at least two anchors and an elongated stabilizer. The anchors each have means to hold the anchor to the bone, and include receiving means which receive the stabilizer as well as securing means which cooperate with the receiving means by means of the interaction of mating threads to cause the application of compression on the stabilizer into the receiving means.
U.S. Pat. No. 5,669,911 relates to a polyaxial pedicle screw. More particularly, this patent relates to a polyaxial orthopedic device for use with rod implant apparatus. The device includes a screw having a curvate head, a locking collar disposed therearound, and a receiving member having a linearly tapered socket in which the screw and the collar are nested. The locking collar is slotted and tapered, and has a semi-spherical interior volume into which the screw head is initially polyaxially held. The receiving member has a transverse channel formed in it for receiving a rod, and an axial bore having a linearly tapered chamber in the bottom portion thereof. The collar is inserted down the bore from the top to seat in the chamber, and the screw is subsequently inserted up through the bottom of the bore and into the collar. The linear taper of the chamber provides a radially inward force on the locking collar when the collar is forced downward therein. This radially inward force causes the locking collar to crush lock against the head of the screw, therein locking the two at the given angulation. It is the placement of the rod in the transverse channel, against the top of the collar, and the subsequent locking down of the rod in the channel which provides the downward force against the locking collar, which in turn locks the screw in its given angulation.
U.S. Pat. No. 5,879,350 relates to a multi-axial bone screw assembly. More particularly, this patent relates to a multi-axial bone screw assembly including a bone screw having a partially spherical head. The bone screw head is truncated at an upper surface in which a tool receiving recess is defined. The assembly includes a receiver member including a central bore that defines a tapered recess to receive a contracting collet carrying the head of the bone screw. The bore of the receiver member also defines a channel communicating with the recess and configured to receive a spinal rod therein. A portion of the channel is threaded to receive a set screw above the rod. The assembly also includes a contracting collet disposed between the rod and the head of the bone screw. The collet defines a partially spherical recess to receive the head of the bone screw, and includes deflectable fingers that substantially surround the screw head. As the set screw is tightened into the receiver member, the set screw compresses the rod against the collet, which presses the collet into the tapered recess of the receiver member, thereby deflecting the fingers of the collet against the bone screw head.
U.S. Pat. No. 6,063,090 relates to a device for connecting a longitudinal support to a pedicle screw. More particularly, this patent relates to a device used to connect a longitudinal support to a pedicle screw by an accommodating head having a channel to accommodate the longitudinal support, wherein it is possible to freely choose from or mix laterally open, top open or closed accommodating heads. A top open accommodating head facilitates, for example, insertion of the longitudinal support, whereas a lateral opening enables lateral corrections. The pedicle screw and the accommodating head are connected via a conical collet chuck in the accommodating head and by a spherical head on the pedicle screw.
U.S. Pat. No. 6,582,436 relates to a device for connecting a longitudinal support to a bone anchor. More particularly, this patent relates to a device for connecting a longitudinal support to a bone anchor having a rounded head. The device includes a body defining a chamber for receiving the rounded head of the bone anchor and a first channel for receiving the longitudinal support. Further, a first sleeve is slidable over the body for compressing the chamber, a second sleeve is slidable over the body for biasing the longitudinal support against the first sleeve, and a fastener is operatively associated with the body for biasing the second sleeve toward the first sleeve. The forces exerted on the second sleeve by the fastener are transferred to the first sleeve in a plane perpendicular to the central axis. Preferably, the longitudinal support contacts the first sleeve at first and second contact points or zones and one of the sleeves includes at least one extended portion for contacting the other sleeve at least one additional contact point or zone.
U.S. Pat. No. 6,660,004 relates to a multi-axial bone screw assembly. More particularly, this patent relates to a bottom-loading multi-axial bone anchor apparatus. The apparatus includes a receiver member, a crown member, a bone anchor and a retaining member. The receiver member defines an upper opening and a lower opening, which may form part of the same opening, a channel, and a groove. The crown member and bone anchor are loaded into the lower opening of the receiver member, and the retaining member fits around the bone anchor and into the groove in the receiver member. The bone anchor is capable of multi-axial positioning with respect to the receiver member. An elongated member is placed in the channel of the receiver member, contacting the crown member, and a compression member is applied via the upper opening. The compression member presses down on the elongated member, which presses down on the crown member and locks the bone anchor between the crown member and the retaining member.
U.S. Pat. No. 6,740,086 relates to a screw and rod fixation assembly and device. More particularly, this patent relates to a screw and rod fixation assembly for fixing a screw and, optionally, a rod. The screw and rod fixation assembly includes a screw, fixing mechanism, a substantially annular ring, rod seating mechanism, and locking mechanism.